Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751431AbdGYSze (ORCPT ); Tue, 25 Jul 2017 14:55:34 -0400 Received: from mail.kernel.org ([198.145.29.99]:51136 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbdGYSzd (ORCPT ); Tue, 25 Jul 2017 14:55:33 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B2DF822B5D Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=jaegeuk@kernel.org Date: Tue, 25 Jul 2017 11:55:32 -0700 From: Jaegeuk Kim To: Yunlong Song Cc: chao@kernel.org, yuchao0@huawei.com, sylinux@163.com, miaoxie@huawei.com, bintian.wang@huawei.com, linux-fsdevel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH] f2fs: let __get_victim successfully get a segno in corner case Message-ID: <20170725185532.GA36902@jaegeuk-macbookpro.roam.corp.google.com> References: <1500033432-57620-1-git-send-email-yunlong.song@huawei.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500033432-57620-1-git-send-email-yunlong.song@huawei.com> User-Agent: Mutt/1.8.2 (2017-04-18) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4850 Lines: 140 On 07/14, Yunlong Song wrote: > Suppose that the valid blocks of each section are all over sbi->fggc_threshold, > and even has_not_enough_free_secs is true, f2fs_gc cannot do its job since the > no_fggc_candidate always returns true. As a result, the reserved segments can be > used up, and finally there is no free segment at all, and get_new_segment cannot > get a free segment, filesystem will trap into a wrong status. > > To fix this, we record the segno which has a rough minimum cost and return it to > __get_victim to continue f2fs_gc's job. > > Signed-off-by: Yunlong Song > --- > fs/f2fs/gc.c | 19 ++++++++++++++----- > fs/f2fs/segment.h | 17 ++++++++++++++--- > 2 files changed, 28 insertions(+), 8 deletions(-) > > diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c > index fa3d2e2..965e783 100644 > --- a/fs/f2fs/gc.c > +++ b/fs/f2fs/gc.c > @@ -178,6 +178,8 @@ static void select_policy(struct f2fs_sb_info *sbi, int gc_type, > p->offset = 0; > else > p->offset = SIT_I(sbi)->last_victim[p->gc_mode]; > + > + p->min_cost_r = UINT_MAX; > } > > static unsigned int get_max_cost(struct f2fs_sb_info *sbi, > @@ -194,7 +196,7 @@ static unsigned int get_max_cost(struct f2fs_sb_info *sbi, > return 0; > } > > -static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) > +static unsigned int check_bg_victims(struct f2fs_sb_info *sbi, struct victim_sel_policy *p) > { > struct dirty_seglist_info *dirty_i = DIRTY_I(sbi); > unsigned int secno; > @@ -208,11 +210,12 @@ static unsigned int check_bg_victims(struct f2fs_sb_info *sbi) > if (sec_usage_check(sbi, secno)) > continue; > > - if (no_fggc_candidate(sbi, secno)) > + p->cur_segno_r = GET_SEG_FROM_SEC(sbi, secno); > + if (no_fggc_candidate(sbi, secno, p)) > continue; > > clear_bit(secno, dirty_i->victim_secmap); > - return GET_SEG_FROM_SEC(sbi, secno); > + return p->cur_segno_r; > } > return NULL_SEGNO; > } > @@ -332,7 +335,7 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, > > last_victim = sm->last_victim[p.gc_mode]; > if (p.alloc_mode == LFS && gc_type == FG_GC) { > - p.min_segno = check_bg_victims(sbi); > + p.min_segno = check_bg_victims(sbi, &p); > if (p.min_segno != NULL_SEGNO) > goto got_it; > } > @@ -369,8 +372,9 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, > goto next; > if (gc_type == BG_GC && test_bit(secno, dirty_i->victim_secmap)) > goto next; > + p.cur_segno_r = segno; > if (gc_type == FG_GC && p.alloc_mode == LFS && > - no_fggc_candidate(sbi, secno)) > + no_fggc_candidate(sbi, secno, &p)) > goto next; > > cost = get_gc_cost(sbi, segno, &p); > @@ -403,6 +407,11 @@ static int get_victim_by_default(struct f2fs_sb_info *sbi, > trace_f2fs_get_victim(sbi->sb, type, gc_type, &p, > sbi->cur_victim_sec, > prefree_segments(sbi), free_segments(sbi)); > + } else if (has_not_enough_free_secs(sbi, 0, 0)) { > + p.min_segno = p.min_segno_r; > + if (p.alloc_mode == LFS && gc_type == FG_GC) > + clear_bit(GET_SEC_FROM_SEG(sbi, p.min_segno), dirty_i->victim_secmap); It seems you want to give a victim segment which has valid blocks larger than fggc_threshold. fggc: 507 reserve: 462 cnt_full: 25182 over: 25912 (>= fggc) less: 870 (< fggc) What is ovp segments? It looks like there are 870 candidates for FG_GC, and GC with 103 segments must give 104 free segments in the worst case. Is there a problem on p.max_search? Thanks, > + goto got_it; > } > out: > mutex_unlock(&dirty_i->seglist_lock); > diff --git a/fs/f2fs/segment.h b/fs/f2fs/segment.h > index 6b871b4..7d2d0f3 100644 > --- a/fs/f2fs/segment.h > +++ b/fs/f2fs/segment.h > @@ -169,6 +169,9 @@ struct victim_sel_policy { > unsigned int ofs_unit; /* bitmap search unit */ > unsigned int min_cost; /* minimum cost */ > unsigned int min_segno; /* segment # having min. cost */ > + unsigned int min_cost_r; /* rough minimum cost */ > + unsigned int min_segno_r; /* segment # having rough min. cost */ > + unsigned int cur_segno_r; /* segment # rough process is handling */ > }; > > struct seg_entry { > @@ -743,11 +746,19 @@ static inline block_t sum_blk_addr(struct f2fs_sb_info *sbi, int base, int type) > } > > static inline bool no_fggc_candidate(struct f2fs_sb_info *sbi, > - unsigned int secno) > + unsigned int secno, struct victim_sel_policy *p) > { > - if (get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true) >= > - sbi->fggc_threshold) > + unsigned int cur_cost; > + > + cur_cost = get_valid_blocks(sbi, GET_SEG_FROM_SEC(sbi, secno), true); > + if (cur_cost >= sbi->fggc_threshold) { > + if (p->min_cost_r > cur_cost) { > + p->min_cost_r = cur_cost; > + p->min_segno_r = p->cur_segno_r; > + } > return true; > + } > + > return false; > } > > -- > 1.8.5.2